This request is for a Bio-Rad Confocal Scanning Laser Microscope System. It will be used in conjunction with a Nikon Optiphot microscope equipped with episcopic fluorescence optics already in place in the Dept. of Anatomy at the Medical College of Ohio. The system will significantly enhance the research programs of ten major users, seven of whom are conducting N.I.H.-funded research projects. The microscope system will also be employed by four other users, three of whom will use it in N.I.H.-supported research. The microscope system will be employed in several distinctly different ways. Dr. Rhoades will use it primarily for the reconstruction of fluorescently-labelled primary afferent axons in fetal rats. Drs. Mooney, Chiaia, and Dun will employ it to assist in the reconstruction of neurons that are filled with Lucifer yellow in both in vitro and "dead-slice" preparations. Drs. Dun and Godfrey will employ the microscope system to reconstruct distributions of transmitters and transmitter-related enzymes in neural tissue. Drs. Lane, Mellgren, Morse, Budd, Pansky, Selman, and Chakraborty will employ the microscope to assist in defining the subcellular locations of antigens recognized by polyclonal and monoclonal antibodies and Dr. Wall will use it in the reflected light mode to assist in the reconstruction of the central terminations of horseradish peroxidase-labelled peripheral nerves in normal and nerve-damaged monkeys. Dr. Goldblatt will use the system for localization of new agents being developed for photodynamic tumor therapy and to assess the effects of such therapy upon the vascularization of tumors. The Bio-Rad system is-the best instrument available for the applications outlined in the preceding paragraph. The investigators whose projects comprise this application have evaluated the systems developed by Bio-Rad, Sarastro, and Zeiss and the performance of the Bio-Rad confocal microscope was superior to the other two systems. The preliminary data included in the application were obtained using the Bio-Rad microscope. The Medical College of Ohio has a strong institutional commitment to the acquisition and maintenance of this microscope system. A highly experienced and state-funded technician, Ms. Patricia McCann, will oversee the day-to-day operation of the microscope and a room in the Dept. of Anatomy will be renovated to house the system. The Medical College has also agreed to pay the service contract for the instrument if it is purchased.